how to restore a logical partition to it's original ext4 format

view story

http://unix.stackexchange.com – This question is following Unable to mount /home/ partition after reinstalling grub after reinstalling windows 7 where the diagnostic was that installing windows 7 deleted my /home partion, lovingly call /dev/sda3. Since almost nothing have been done with this computer since the incident, we can expect that the content of the partition is still intact and that it is only unusable for the moment. The mission is to try to rescue the files that were inside this partition by restoring it to it's original ext4 format. Does anyone know how to proceed? (HowTos)